A hybrid vehicle described in Patent Document 1 includes an engine which drives a generator and a drive motor which drives driving wheels and includes a drive battery that stores electric power from the generator and which supplies the electric power to the drive motor. FIG. 22 shows diagrams showing variations of various data in a process before electric power is started to be generated in the hybrid vehicle described in Patent Document 1. A drive system control unit provided in the hybrid vehicle described in Patent Document 1 calculates a charged/discharged power Wbat of the drive battery based on a current Ibat and a voltage Vbat of the drive battery and calculates an accumulated power value Ebat in which the charged/discharged power Wbat is accumulated. Following this, the drive system control unit calculates an accumulated value variation rate DEbat which is a variation rate of the accumulated power value Ebat for each calculation cycle Tpre and thereafter sets a generation threshold Gsoc based on the accumulated value variation rate DEbat. As shown in FIG. 22, the generation threshold Gsoc increases as the accumulated value variation rate DEbat increases.
When it determines that the generation threshold Gsoc which is reset for each calculation cycle Tpre is below a state of charge SOC, the drive system control unit starts generation by the generator. As a result, not only can the exhaustion of electric power in the drive battery be avoided, but also the generation cycle of the generator can be set long. The timing at which the generation is stopped occurs only when the state of charge SOC reaches a predetermined upper limit level.
Patent Document 2 discloses a generation control apparatus for a hybrid electric vehicle which can generate a sufficient amount of electric power in a good response to a request for high output made to a motor. FIG. 23 is a time chart which shows one example of a control result of a generation control by the generation control apparatus described in Patent Document 2. The generation control apparatus starts a normal output generation (P(G)=P1) by a generator when a charged level SOC of a battery is equal to or smaller than a generation start value SOCsta and continues this normal output generation until the charged level reaches a generation end value SOCend. As this occurs, when a required consumed electric power Pm of a drive motor which is detected by a required consumed electric power detection device is equal to or larger than a set value Ph, a high output generation (P(G)=P2) which generates a higher output than the output generated by the normal output generation is executed in place of the normal output generation.